Circuit breakers are special switches that are usually designed for high currents and can carry not only operating currents and small overload currents, but also, in the event of faults, high overload and short circuit currents, maintain these fault currents for a specified time and break them again. A circuit breaker has the task in particular of interrupting the current flowing through the circuit breaker.
The current is generally interrupted by way of a movable, usually pivoted contact element. To open the contact, the movable contact element is moved away from a fixed contact element, one or more arrangements of movable and stationary contact elements possibly being present in a circuit breaker. The unit comprising movable and fixed contact elements is called the switch pole or pole cassette. A switch pole generally has a double-shell housing composed of two shells of at least approximately symmetrical design. During assembly of a switch pole, the components are first installed in the lower shell and finally the upper shell is placed on top like a lid.
In this connection, DE 10 2008 050 754 A1 discloses a generic switch pole. Inside the switch pole a pivoted contact element is provided via which a current can flow from a first contact element fixed in the housing to a second contact element fixed in the housing when the contacts are closed. If such a current becomes excessively high, swiveling of the pivoted contact element is initiated via the slot motor by the magnetic field produced by the current itself so that its contact arms move away from the contact elements fixed in the housing. In addition, an arc is struck which is deflected into an arcing chamber in the switch poles. Said deflection of the arc is assisted by ferromagnetic metal pieces which drive the arc into the arc chutes of the switch pole in the desired manner.
The switch poles of modern circuit breakers are often encapsulated using pole cassettes. Instead of pre-assembled arc chutes, arc chutes consisting of individual splitter plates and arc runners are often installed.
The switch pole described in DE 10 2008 050 754 A1 has arc chutes including individual splitter plates and arc runner plates. The splitter plates are each held at one end in a slot in one half of the switch pole housing and with the other end in a corresponding slot in the second, opposite half of the switch pole housing. Assembly once again takes place by first inserting the components into the lower shell and then placing the upper shell on top like a lid. The slots engage around part of the plates, while the arc chutes of the switch pole are formed by the exposed areas of the plates.
The problem with the known design of pole cassettes/switch poles is often that during assembly, particularly when placing the second pole shell on top, the splitter plates must engage exactly in the slots of the pole shell being applied. Assembly often proves to be difficult, as the slots particularly in duroplastic materials must be manufactured with a certain oversize, which means that the splitter plates tend to tilt when they are inserted in the slots. This makes it difficult to insert the splitter plates into the slots of the pole shell applied from above, which makes the assembly of the pole cassette/switch pole significantly more difficult.
For this reason it is often necessary to hold and guide the plates during assembly in such a way that the pole cassette can be closed without difficulty. In this respect the large number of individual splitter plates and arc runner plates as well as other components forming the current path poses a particular challenge for closing the pole cassette.